US3588904A - Antenna construction with low q radiators - Google Patents

Abstract

AN ANTENNA CONSTRUCTION WHEREIN THE RADIATOR ELEMENTS OF A RADIATING ARRAY INCLUDE SIDE-BY-SIDE ELONGATED PORTIONS WHICH HAVE BEEN SPREAD APART INTERMEDIATE THEIR ENDS SO THAT THE SEPARATION BETWEEN THE TWO ELONGATED PORTIONS OF EACH RADIATOR ELEMENT IS AT ITS GREATEST IN A GENERAL REGION MIDWAY BETWEEN THE CABLE-SUPPORTED OUTER AND INNER ENDS OF THE RADIATING ELEMENT.

Description

United States Patent Inventor Harry C. Broyles Sunnyvale, Calif.

Appl. No. 770,285

Filed Oct. 24, 1968 Patented June 28, 1971 Assignee Granger Associates Palo Alto, Calif.

ANTENNA CONSTRUCTION WITH LOW Q RADIATORS 6 Claims, 15 Drawing Figs.

U.S.Cl 343/792.5,

343/807, 343/812, 343/886 Int. Cl ..B01q 11/10 Field at Search 343/7925,

[56] References Cited UNITED STATES PATENTS 2,524,993 10/1950 Rumsey 343/807 3,165,748 1/1965 Woloszczuk 343/7925 3,271,774 9/1966 Justice 343/7925 3,470,559 9/1969 Radford 343/7925 Primary Examiner- Eli Lieberman Attorney-Flehr. Hohbach, Test, Albritton & Herbert PATENTEU JUN28 19m SHEET 1 [IF 5 INVENTOR. HARRY C. BROYLES ATTORNEYS PATENTEU M28 as?! SHEET 2 1F 5 INVENTOR.

HARRY C. BROYLES ATTORNEYS PATENT0JuH28|9n 3,588,904

" SHEET 3 [IF 5 INVENTOR HARRY c. BROYLES ii ANTENNA cons'jrjaucrnos wrra sow o aanm'rons ascsoaouno or THE mvanrron This invention pejrt ains to antenna structures. The invention is particularly useful, as a log periodic antenna of the type characterized by flexible dual wire radiator elements as may be supported at their ends by a flexible catenary cable.

As is Itnown, it has long been a general objective in providing log periodic antennas and other similar types of antenna to reduce the bullt an physical scope of the antenna so that, among other things, the occupied land space required for the installation will be minimized.

Where weather conditions are particularly adverse, it is also desirable to keep the antenna size to a minimum so as to reduce the expense land size of the supporting structure as required, for example, to maintain a radiating array atop a support tower. Thus,,as is known, antennas of this type may be subject to icing conditions whereby the sail area of the radiating array becomes unmanageable and imposes serious burdens on the supporting strdcture.

OBJECTS It is a general objefct of the present invention to provide an improved antenna structure and, more particularly, to provide such an improved antenna structure wherein the scope and size of the antenna is generally smaller for comparable per formance so as to require minimum support structure for the array.

It is another obje c i of the invention to provide an antenna structure of the above type wherein the Q of the radiator elements is reduced and thereby permits the radiating array to be commensurately reduced in size for comparable performance.

Other objects of the invention will become more readily apparent from the following detailed description when considered in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION According to the structures herein disclosed, an antenna array has been provided having radiator elements comprised of side-by-side spaced elongated portions carried from their outer ends and coupled to feed line means at their inner ends. The array is characterized in the fact that intermediate the ends of the adjacent radiator portions, means have been provided for spreading the radiator portions so as to reduce the Q of the radiator element.

In the above manner, the extent of the radiator element can be reduced with the advantages attendant such reduction in the size of the array. Thus, less sail area is exposed to icing and weather conditions, catenaries supporting the array can be of smaller diameter, and the required stretching forces applied to the catenaries can be reduced. Also, less occupied land space will be involved, as well as lighter weight materials and structures.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic plan view of an antenna array construction according to the invention;

FIG. 1A is a schematic perspective view diagrammatically showing an antenna construction according to the invention;

FIG. 2 shows, in enlarged detail, a plan view of a single radiator element of the type shown in FIG. I;

FIG. 3 shows, in enlarged detail, a plan view taken along the line 3-3 of FIG. I;

FIG. 4 is a side elevation view of FIG. 3, partially broken away;

FIG. 4A is a view similar to FIG. 4 showing another embodiment of the FIG. 6 construction;

FIG. 5 is an enlarged detail plan view taken along the line 5-5 of FIG. I;

FIG. 6 is a front elevation view of a portion of FIG. 5;

FIG. 7 is an enlarged side elevation detail view taken along the line 7-7 of FIG. ll;

FIG. 3 and 9, both taken along the line 3-8 of FIG. I, are enlarged detail plan and front elevation views, respectively;

FIG. I0 is a schematic plan view of an antenna construction according to another embodiment of the invention;

FIG. II is an enlarged detail plan view taken along the line II-lll of FIG. I0;

FIG. I2 is a side elevation view ofa portion ofFlG. II;

FIG. I3 is a schematic perspective view of an antenna construction according to another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Having in mind the above general summary of the invention and with reference particularly to the accompanying drawings, a detailed description of an antenna structure according to the invention can be more clearly understood with reference to FIGS. I and IA. Thus, a support tower II carries a log periodic, transposed dipole array I2 comprised of a plurality of spaced elongated flexible radiator elements 13. Each radiator element I3 includes a pair of elongated flexible porlions Id, Id.

The array 112 is supported atop tower II by a pair of catenary cables I7, Iti carried by the ends of three equiangular support booms I9, 2I, 22, respectively. Cables I7, I8 support the outer ends oieach of the radiator elements I3 while the inner ends of radiator elements I3 are operatively coupled to feed lines 23, 24. The booms are inclined upwardly.

Suitable guy wires 26 support the tower II in an upright position while a mast extension portion 27 provides an anchoring point for guy lines 23 acting to support the booms 19, H, 22 from above. Thus, array 12 lies above the upwardly inclined booms.

With the foregoing arrangement in mind, there has been disclosed herein means for interconnecting adjacent radiator elements I3 along a line of connecting, points defined intermediate the outer and inner ends of the radiator elements so as to provide a predetermined spacing between the portions Id, I6 of each radiator I3. The spacing is at its greatest for each radiator I3 in the intermediate zone located between the outer and inner ends of the radiators and, for example, preferably is substantially midway between the outer and inner ends of each radiator element. Accordingly, by inspection of FIG. 1, the aforementioned line of interconnecting points is designated by the phantom line 29.

By spreading the two portions 14, IIIS of each radiator element from each other, it is possible to significantly reduce the Q of each radiator element and in that manner broaden the bandwidth of the active region of the radiating array.

As is known, the Q represents a figure of merit of an energy storing system equal to:

21r(average energy stored energy dissipated per half-cycle).

The above fonnulation has been reduced for inductance whereby Q=,,L/R where R is the equivalent series resistance of the inductors. For capacitance, Q is equal to 1/,,,CR.

The outer ends of elements I3 are supported by connection to cables I7, I3 as shown in enlarged detail in FIGS. 2, 3 and 4 as now to be described.

Portions M, 116 of an element 13 are defined by separate reaches of a single continuous electrically conductive flexible cable material such as copper or aluminum wire.

A metal strap forms a stirrup 31 engaging the outer loop formed between portions M, 16 and the ends of strap or stirrup III are bolted or otherwise suitably secured to an end of an electrical insulator 32. Insulator 32 is of suitable material whereby it provides considerable physical strength for supporting the outer end of element 13 and suitable insulator material is, of course, well known to the trade. For example, the material of insulator 32 can be alumina.

The other end of insulator 32 carries a pair of support links 33 pivotally secured to bar 32 and also to lobes 34 formed on each of a pair of relatively thick plate portions 36 forming a cable clamp adapted to be secured firmly to one of the catenary cables I7 I8. Each plate 36 includes a recess portion 38 whereby screws 39 can draw the confronting side faces of plates 36 tightly together to engage cable 18.

Lobe portions 34 may also be drawn tightly together whereby a bolt 41 can pivotaliy support the end of each of the two links 33. Various means may be arranged for securing the outer end of each radiating clement I3 to be carried by a catenary cable such as cables l7, I8 and another embodiment of the scheme for supporting the outer ends of elements 13 is shown in FIG. 4A.

In FIG. 4A, parts similarly employed to those previously described are numbered the same but are provided with prime marks However, while the upper portions of plates 36 may be drawn tightly together with screws 39 so as to clamp tightly against cable 18, the lobes 42 are spaced somewhat apart whereby they provide an accommodating space or passage 43 through which a loop formed in the outer end of a radiating element 13' can be carried directly by clamp 37'. It is to be understood, however, that clamp 37 will, accordingly, be constructed of an insulating material having sufficient rigidity to provide the support involved herein. One such material, for example may be alumina or other high strength insulating material.

Thus, the portions 14', 16' of a given radiator element 13 may be clamped together by a swage fitting 46 to provide a loop to engage the shank of a bolt 44 carried by the spaced lobes 42. In the foregoing manner, it is apparent that the outer ends of each radiator element l3 may be supported in an insulated fashion from one of the catenary cables I7, 18.

As shown best in FIGS. 8 and 9, the inner ends of each radiator element 13 are operably coupled to receive radiation from feed lines 47, 48 and it is to be understood that the pattern of selection of making connections between the radiator elements 13 and feed lines 47, 48 will be dictated by the type of antenna operation desired. For example, in one pattern, it may be desirable to connect successive radiator elements 13 located on one side of feed lines 47, 48 alternately to feed lines 47, 48. Thus, every other one of the radiator elements 13 lying on one side of the feed lines will be connected to in common to the same feed line.

Referring to FIGS. 8 and 9, it will be readily evident that the inner ends of each radiator element are formed to provide a loop 49 by merely clamping a swage fitting 51 about the bitter .ends 52, 53 of portions 14, 16.

Thus, loop 49 engages a stirrup 54 which, in turn, is bolted to one end of an insulative spacer bar 56. In order to provide electrical connection from feed lines 47, 48 to the radiator elements 13, swage connections 57 are carried by the feed lines, such as 47, and, in turn, bolted to a connector tab por tion 58 of stirrup 54. In this manner, electrical connection is positively made between feed lines 47, 48 respectively to the inner ends of each radiator element 13.

Means serving to reduce the Q of the radiators by drawing their respective portions 14, I6 apart whereby, for comparable performance, a smaller radiating array can be employed includes the interradiator connectors 62 (FIG. comprised, for example, simply of an insulator bar 63 of suitably rigid insulative material such as noted above.

The opposite ends of each bar 63 are coupled to straps 64, 66 whereby each strap 64, 66 respectively engages a bight of a portion 16, 14 of adjacent radiator elements 13.

Each connector assembly 62 forms an interconnecting point whereby all of the points lying on one side of feed lines 47, 48 define line 29 lying in a region generally in a middle zone between the opposite ends of each radiator element 13.

' At the leading end of array 12, the ieadingmost radiator element 13b is supported in the foregoing manner by one of the interradiator connectors 62 and by the means shown in FIG. 7 is carried by the leading support spar 67. Thus, a rigid insulator bar 68 is supported by a U-bolt 69 stone and and employs a shsckle 71 at the other end to engage the radiator portion I6 of element l3b.

At the rear end or "back" of array 12, a parasitic element 72 serves to tension the rear portion of feed lines 47, 48 while the rear half of the rearmost radiator element 13c may extend straight across the array in its natural position since the drawing of the forward half of such element provides sufficient spacing between the two conductive portions 14, 16 of element [3c to permit the elimination of means for drawing away the rear portion.

According to another embodiment, as shown in FIG. I3, a radiating array 76 of similarly arranged diamond-shaped radiating elements 77 is oriented in a single upright plane as distinguished from the substantially horizontal plane shown in FIG. I. Thus, rather than to carry the radiating array atop a support tower, such as tower l1, it may be desirable under certain circumstances to provide a so-called curtain" antenna arrangement wherein the array is oriented upright.

Referring to FIG. 13, a support tower 78, suitably guyed by lines 79 supports array 76 by means of a single catenary cable 81 carried between the upper end of tower 78 and the upper end of a support post 82. In the region of post 82, a balun 83 is electrically coupled to the feed lines 84, 86. Support means for carrying the inner and outer ends of each radiator element 77 are similar to those shown in the embodiment in FIG. 1 and need not be repeated at this time.

A further embodiment of the invention is shown in FIGS. 10 and II and 12 wherein each radiator element 87 includes a rigid spreader link 88 which completes the interstices otherwise found in the line of support 29 defined by the interconnecting points formed between adjacent radiator elements. In this manner, the substantial equivalent of an interior supporting cable or catenary as defined by line 29 serves to provide additional catenary cable support to the array of elements 13 to provide advantages which are disclosed in copending US. application Ser. No. 648, 475 assigned to the assignee herein.

The links 88 are preferably of a nonconductive material. If made of conductive material, the material of the links 88 should be the same as the radiator elements to avoid any problems of electrolysis.

Means for introducing the links 88 into line 29 appear in FIGS. 11 and 12 in more particular detail. Thus, each link 88 is engaged at its opposite ends by opposed pairs of U-shaped clamps 91 bolted thereto in a manner to retain a bight of one of the portions 87a, 87b of a radiator element 87 (FIG. 10). In addition, and to provide the interconnection between adjacent radiators 87, rigid connecting bar 92, comparable to bar 63, (noted in parenthesis) is bolted to the opposed ends of the two pairs of clamps 91.

In the foregoing way, a major portion of the load of the array carried by the catenary cable means may be supported by the interior supporting cable defined by the alternately occurring rigid spreader links 88 and interradiator connecting bars 92. Thus, as shown in phantom lines in FIG. 2, a rigid spreader link 94 (comparable to bars 92) may serve to complete the foregoing style of interior catenary cable" as defined by the links and interconnecting bars.

The foregoing arrangement serves to provide an overall array occupying less land space while providing comparable performance.

From the foregoing, it will be readily apparent that a radiating construction has been provided wherein the radiating elements are comprised as a four-sided flexible configuration including opposed pairs of corners. All the radiators are oriented to lie in a single common "plane" (to the extent that the sagging nature of the arrayelements may be considered to form a plane), and the predetermined spacing between the corners of one pair is sufficient to substantially reduce the Q of the radiator element associated therewith so as to permit a reduction in the array size while obtaining comparable performance.

Iclaim:

I. In an antenna structure, a radiating array of elongated radiating elements having first and second ends thereof, feed line means operably coupled to a first end of each of said radiating elements, and means common to and supporting a plurality of said radiating elements at second ends thereof,

each of said radiating elements including a pair of elongated laterally spaced radiating portions, and means interconnecting adjacent portions of adjacent radiating elements at a position intermediate said first and second ends thereof to maintain a predetermined spacing between the portions of each of a plurality of said radiators, the last named means causing said spacing to be at its greatest in an intermediate zone between the first and second ends of the radiators to reduce the Q of the radiators.

2. In an antenna having a support tower and a radiating array carried by the tower, said array including a plurality of spaced elongated flexible radiator elements, each element including a pair of elongated flexible portions, laterally spaced, flexible catenary cable means supporting outer ends of said radiator elements, feed line means coupled to the inner ends of said elements, and means for interconnecting adjacent radiator elements along a line intermediate the outer and inner ends of said elements to provide a predetermined spacing between the said portions of radiators, said spacing being at its greatest intermediate the outer and inner ends of said radiators.

3. In an antenna according to claim 2 wherein points of interconnection are defined between the last named means and the radiator elements at locations between the inner and outer ends thereof, said points of interconnection serving to draw on of said portions of each pair of radiator elements relatively away from the other in supporting said elements whereby said line of interconnections acting through said one of each pair of portions serves to efiectively broaden the radiators intermediate the inner and outer ends of said radiator elements to provide said predetermined spacing.

4. In an antenna construction according to Claim 3 wherein said cable means includes a pair of laterally spaced cables serving to support the outer ends of radiator elements, said radiator element portions serving to define polygonal areas constituting a radiator element, said polygonal areas being disposed substantially in a common plane, corners of said polygonal areas forming single points of support for connection with respect to said catenary cable means and said feed line means at the inner and outer ends of the radiator elements.

5. in an antenna according to claim 3 further including a spacer disposed between the pair of portions of each radiator element at said points of interconnection to provide a line of support for said array intermediate the ends of each radiator element.

6. In an antenna structure, a radiating construction comprising a plurality of radiators, each of said radiators including means forming a four-sided configuration lying substantially in a single plane with first and second pairs of opposed comers, feed means operatively coupled at one comer of said first pair of comers, means supporting a number of said radiators to form a log periodic array in which all of the radiators lie sub stantially in a single plane common to each, said support means including means for maintaining a predetermined spacing between said second pair of corners, the spacing between said second pair of corners being sufficient to substantially reduce the Q of the radiator.

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